Purpose: The goal of this study was to document the incidence of anterior cruciate ligament (ACL) tears and possible risk factors for these injuries in a large population of young, athletic subjects.
Methods: The authors retrospectively reviewed the US Naval Academy's database of midshipmen admitted in 1999 and 2000 (n = 2,345) and prospectively followed until graduation 4 years later or disenrollment. Excluded were 658 who had a history of preadmission ACL injury or surgery, those without initial radiographs or documented baseline height and weight, or those who had documented contact ACL injuries. Therefore, 1,687 subjects comprised the study group. Standard radiographic measurements, including condylar width, notch width, and femoral notch width index (notch width divided by condyle width), were obtained for all subjects. Statistical analyses were used to determine differences between injured and uninjured subjects.
Results: The overall incidence of non-contact ACL injury was 2.9% (37 men, 12 women). The average BMI was 25.6 and 24.4 kg/m(2) for the injured and uninjured groups, respectively (P < 0.05). Although femoral notch width alone was not associated with non-contact ACL injuries, subjects with higher than average BMI in combination with narrow notch width were at significant risk for ACL injury (P = 0.021).
Conclusions: Elevated BMI combined with narrow notch width may predispose young athletes to non-contact ACL injury.
Level of evidence: Retrospective comparative study, Level III.